CliC Newsletter - Ice and Climate No. 29

Ice and Climate Newsletter Volume 29: April 2018

ISSN 1811-0843

In this issue:

Our April 2018 newsletter includes three science features: one on potential ice-free summers in the Arctic depending on small climate warming range; another looks at the ice sheet model initialisation experiments initMIP-Greenland; and the third highlights the Open Global Glacier Model (OGGM) v1.0. This issue also contains summaries from various CliC events held at the AGU Fall Meeting 2017 and since the beginning of the year, including the 14th Session of the CliC Scientific Steering Group; the 2017 CliC Annual Report; and a list of our upcoming workshops and meetings.

In this newsletter, we also welcome our new CliC Co-Chair Fiamma Straneo from the Scripps Institution of Oceanography at the University of California San Diego.

Lastly, we would like to take this opportunity to thank our out‐going CliC co‐chair Gerhard Krinner for guiding our work the last 5 years. Gerhard will stay involved in CliC as the lead of our ESM-SnowMIP Targeted Activity.

Probabilities of reaching an ice-free Arctic at least once as function of time for the different scenarios, shown in the legend. The meaning of the probabilities is given in grey according to the IPCC convention.A range of less than one degree Fahrenheit (or half a degree Celsius) of climate warming over the next century could make all the difference when it comes to the probability of future ice-free summers in the Arctic, new CU Boulder research shows.

The findings, which were published in the journal Nature Climate Change, show that limiting warming to 2.7 degrees Fahrenheit (1.5 degrees Celsius) would reduce the likelihood of an ice-free Arctic summer to 30 percent by the year 2100, whereas warming by 3.6 degrees Fahrenheit (2 degrees Celsius) would make at least one ice-free summer certain.

“I didn’t expect to find that half a degree Celsius would make a big difference, but it really does,” said Alexandra Jahn, author of the study and an assistant professor in CU Boulder’s Department of Atmospheric and Oceanic Sciences and a fellow in the Institute of Arctic and Alpine Research (INSTAAR). “At 1.5 degrees Celsius, half of the time we stay within our current summer sea ice regime whereas if we reach 2 degrees of warming, the summer sea ice area will always be below what we have experienced in recent decades.”

The study used simulations from the Community Earth System Model (CESM) run at the National Center for Atmospheric Research (NCAR) and examined warming scenarios ranging from 1.5 degrees Celsius all the way to 4 degrees Celsius (7.2 degrees Fahrenheit) by the end of the century. The lower bound of the study is an important benchmark worldwide; in 2015, the international Paris Climate Agreement set a global target of constraining warming to 1.5 degrees Celsius.

Arctic sea ice extent has declined overall in recent years with increasing global temperatures, but the effects of future warming remain uncertain. The new findings illustrate that different scenarios of carbon dioxide (CO2) emission levels lead to drastically different results for Arctic summer sea ice.

This dataset allows us to predict how soon we’re likely to see ice free conditions as well as how often,” said Jahn. “Under the 4-degree Celsius scenario, we would have a high probability of a three-month ice free period in the summer months by 2050. By the end of century, that could jump to five months a year without ice. And even for half that warming, ice-free conditions of up to 2 month a year are possible by the late 21st century.”

But, Jahn continued, if warming stays at 1.5 degrees Celsius, the probability of ice-free summers would drop by 70 percent, delaying or potentially even avoiding such occurrence altogether.

The significant difference in the results, Jahn said, might provide added incentive for countries to attempt to hit the 1.5-degree Celsius warming target in order to preserve current ecological conditions.

“The good news is that sea ice has quick response times and could theoretically recover if we brought down global temperatures at any point in the future,” said Jahn. “In the meantime, though, other ecosystems could see permanent negative impacts from the ice loss, and those can’t necessarily bounce back.”

Common ice mask of the ensemble of models in the initMIP-Greenland intercomparison. The colour code indicates the number of models (out of 35 in total) that simulate ice at a given location. Outlines of the observed ice sheet proper and all ice-covered regions (i.e. main ice sheet plus small ice caps and glaciers) are given as black and grey contour lines, respectively.

Earlier large-scale Greenland ice sheet sea-level projections have shown that ice sheet initial conditions can have a large effect on the projections and give rise to important uncertainties.

The goal of the initMIP-Greenland intercomparison exercise is to compare, evaluate and improve initialisation techniques and to estimate the associated uncertainties. initMIP-Greenland is the first in a series of ice sheet model intercomparison activities within ISMIP6 (the Ice Sheet Model Intercomparison Project for CMIP6), a CliC Targeted Activitiy, part of the WCRP Grand Challenge on Melting Ice and Global Consequences.

The authors have compared a wide spectrum of different initialisation techniques used in the ice sheet modelling community to define the modelled present-day Greenland ice sheet state as starting point for physically-based future sea-level change projections. Compared to earlier community-wide comparisons they find better agreement across different models, which implies overall improvement of the understanding of what is needed to produce such initial states.

Example of the OGGM ice thickness estimation workflow applied to Tasman glacier, New Zealand.Despite their importance for sea-level rise, seasonal water availability, and as a source of geohazards, mountain glaciers are one of the few remaining sub-systems of the global climate system for which no globally applicable, open source, community-driven model exists. Here we present the Open Global Glacier Model (OGGM, http://www.oggm.org), developed to provide a modular and open source numerical model framework for simulating past and future change of any glacier in the world.

In this paper, we describe and illustrate each processing step by applying the model to a selection of glaciers before running global simulations under idealized climate forcings. Even without an in-depth calibration, the model shows a very realistic behaviour. We are able to reproduce earlier estimates of global glacier volume by varying the ice dynamical parameters within a range of plausible values. At the same time, the increased complexity of OGGM compared to other prevalent global glacier models comes at a reasonable computational cost: several dozens of glaciers can be simulated on a personal computer, while global simulations realized in a supercomputing environment take up to a few hours per century.

Thanks to the modular framework, modules of varying complexity can be added to the codebase, allowing to run new kinds of model intercomparisons in a controlled environment. Future developments will add new physical processes to the model as well as tools to calibrate the model in a more comprehensive way. OGGM spans a wide range of applications, from ice-climate interaction studies at millennial timescales to estimates of the contribution of glaciers to past and future sea-level change. It has the potential to become a self-sustained, community-driven model for global and regional glacier evolution.

CliC News

Prof. Fiamma Straneo appointed CliC Co-Chair

Prof. Fiamma Straneo was appointed CliC Co-chair on January 1, 2018, for a 3-year period. She is replacing Dr. Gerhard Krinner and will co-chair the CliC Scientific Steering Group together with Dr. James Renwick, appointed in 2017.

Fiamma Straneo is a Professor in Polar Climate and Oceans at the Scripps Institution of Oceanography of the University of California San Diego. Prior to joining Scripps, she was a Senior Scientist at the Woods Hole Oceanographic Institution. She studies the high latitude North Atlantic and Arctic Oceans and their interaction with the atmosphere, sea-ice and the Greenland Ice Sheet. Much of her research has focused on obtaining and interpreting data from the challenging regions at the glaciers’ margins using a variety of platforms such as icebreakers, fishing vessels, helicopters, snowmobiles and autonomous vehicles. Straneo has led over a dozen field expeditions to the Arctic and Greenland.

Fiamma is a fellow of the Leopold Leadership Program, co-chair and founder of the Greenland Ice Sheet/Ocean Science Network (GRISO), a member of the Atlantic Meridional Overturning Circulation Science Team and of the ASOF (Arctic-Subarctic Ocean Fluxes). She received the Sverdrup Award by the Ocean Sciences Section of the American Geophysical Union in 2016. Straneo obtained her Ph.D. in Physical Oceanography from the University of Washington, USA, following a Laurea cum Laude in Physics from the University of Milan, Italy.

The 39th Session of the WCRP (World Climate Research Programme) Joint Scientific Committee (JSC-39) took place at Nanjing University of Information Science and Technology (NUIST) from April 16-20, 2018. The JSC is an annual meeting where the leaders of the WCRP research community discuss progress towards the Programme's objectives and make decisions that will determine the future direction of the organisation.

The Nanjing meeting focused on the revised WCRP Strategy, and the associated recommendations made by the recent WCRP Co-Sponsors review. A full day scientific workshop was also programmed and highlighted emerging research from the local host institution and wider Chinese community as well as international guests.

The WCRP is currently developing a new strategic plan, covering a 10-year time horizon (2019-2029). It will outline the overall strategy and high-level scientific questions that WCRP will address over the next decade. The WCRP Strategic Plan will be written and approved by the JSC and will include extensive consultation and discussion. The strategic plan will be complemented by an implementation plan, which will be a 5-year outline of how the strategic plan will be achieved, with a second instalment to be produced in 2024.

The workshop attracted 30 scientists from China, France, Germany, Japan, Norway, Russia, UK, and USA to present most recent findings on polar low research. The workshop summarized our present understanding of polar lows and mesocyclones as well as mesoscale weather extremes in the Arctic and Antarctic. This includes e.g. mesoscale weather phenomena such as katabatic winds, tip jets, boundary layer fronts, and cold air outbreaks in polar regions. The workshop had the following main themes: Polar low studies using satellite data and in-situ data; climatological aspects of polar lows; polar lows in reanalyses and model simulations; environments for polar low genesis and operational aspects; polar mesoscale weather phenomena and air-sea-ocean interactions. The workshop was concluded by a round table discussion resulting in recommendations for future research and actions.

Polar Organisations provide travel support for ECRs to attend POLAR2018

Through this generous financial support from all contributing organizations, we were able to fund 91 applicants from 27 countries (Australia, Austria, Belgium, Brazil, Canada, Chile, China, Czech Republic, Denmark, France, Germany, Iceland, India, Italy, Japan, New Zealand, Norway, Poland, Portugal, Russia, South Africa, South Korea, Spain, Sweden, Turkey, the United Kingdom and the United States). All recipients have been notified and have accepted their awards. Congratulations to all recipients!

Thank you again to all the funders for making this incredible support possible. Also a big thank you to the reviewers who took their time to help us evaluate all these applications.

The workshop aims at:- reviewing and advancing our understanding of the changes in the cryosphere as well as their environmental, social and economic implications,- fostering knowledge exchange in modelling and assessing such changes, - assessing and improving our approaches in risk mitigation and adaption to the changing cryosphere, and- shedding light on the role of the cryosphere in the context of sustainability for the benefit of our future earth.

An Arctic Sea Ice Prediction Stakeholders Workshop was held as a side-event at the Arctic Frontiers 2018 Conference (http://www.arcticfrontiers.com/) on January 22, 2018, from 15:00 to 18:30, at the Radisson Blue Hotel, in Tromsø, Norway.

The Arctic sea ice prediction community has advanced rapidly in the past decade with many new sea ice forecast products and services which are targeted for different user groups. However, it is still unclear how well end users are able to integrate information from these services into their navigational planning and how they use sea ice forecast information. To improve the uptake and usability of sea ice information supplied by the operational community, there is a need for better engagement and dialogue with a broad range of Arctic stakeholders and a need to tailor new products and services to end user specific requirements.

The organising committee for the Arctic Frontiers workshop assembled a cross-section of forecasters from Europe and North America along with key representatives from the private sector to discuss emerging issues and highlight opportunities. The workshop focused on creating an engaging dialogue and gathering feedback from all participants in order to get a better understanding of current and future user needs.

Some of the overarching questions addressed at the workshop included:- What is the economic value of current forecasting systems?- How are forecasts used in decision making, and if not, then why?- What are the limits and opportunities associated with current forecasting systems?

Going forward the event organisers are looking to establish cooperation opportunities with the participants and to develop a longer-term strategy for continued engagement between these communities. There are many opportunities for improvements in the reliability of sea ice forecasts and an eagerness amongst users to help tailor products that suit their needs. Such dialogue and enhancements should lead to better informed stakeholder decision making, safer passage of vessels and sustainable economic development.

GlacierMIP Workshop at the AGU Fall Meeting, December 11, 2017, New Orleans, USA

--Contributed by Ben Marzeion

A meeting of GlacierMIP was held on December 11, 2017, during the AGU Fall Meeting in New Orleans. Almost all active participants of GlacierMIP were able to join, either in person or by video conference, including two new participants (Philip Kraaijenbrink and Walter Immerzeel from the University of Utrecht, NL). Each participant reported on the progress of modeling for phase II. At least seven global and three regional models confirmed their participation. Goal of phase II is the production of global glacier projections based on homogenized initial and boundary conditions. The results are expected to be available for analysis to the GlacierMIP community in spring/early summer 2018, such that first results can be discussed during the next GlacierMIP meeting, planned for the SCAR/IASC Open Science Conference in Davos in June 2018.

ISMIP6 Workshop at the AGU Fall Meeting, December 10, 2017, New Orleans, USA

--Contributed by Sophie Nowicki

he ISMIP6 annual Pre-AGU meeting focused on a review of current standalone ice sheet model simulation and planning for the next suite of experiments. Our current effort, initMIP-Antarctica, investigates the uncertainty in sea level projections arising from the choice of initialization procedure for ice sheet models. As the initMIP-Antarctica runs have been completed, a preliminary analysis of these results were presented and discussed. The second part of the meeting reviewed the current plans for the ISMIP6-PMIP simulation, the coupled AOGCM-ISM simulations, and how to translate CMIP6 atmospheric and oceanic fields into drivers for the standalone ice sheet simulations. This included presentations of what is possible on the ice sheet model side (for example, how ice sheet models currently implement oceanic forcing), but also presentations on what can be expected from the CMIP6 ocean models. The meeting was attended by 25 participants, with expertise in ice sheet modeling, climate modeling and observationalists in the polar regions.

The Permafrost Carbon Network met for its annual meeting on December 10, 2017, in New Orleans, on the margins of the 2017 AGU Fall Meeting. In the morning, synthesis leads gave short presentations and updated the group on ongoing and new activities. Breakout discussions in the afternoon focused on advancing existing syntheses and brainstorming new ideas and topics. The breakout discussions focused on a) Expert assessment of permafrost; b) Thermokarst: what have we done, what do we know, where are we going; c) Bottom-up estimations of methane emissions; d) Model benchmarking; e) Thaw-induced changes to the permafrost microbiome and the functional implication; f) Bottom-up CO2 flux synthesis; g) Organizing validation data for remote sensing product, and h) Surface water analysis for pan-Arctic permafrost.